Association for Innovation and Biomedical Research on Light and Image (AIBILI), Coimbra, Portugal

Torcato Santos

Association for Innovation and Biomedical Research on Light and Image (AIBILI), Coimbra, Portugal

Isabel Pires

Association for Innovation and Biomedical Research on Light and Image (AIBILI), Coimbra, Portugal

Conceição Lobo

Association for Innovation and Biomedical Research on Light and Image (AIBILI), Coimbra, PortugalInstitute of Biomedical Research on Light and Image (IBILI), Faculty of Medicine, University of Coimbra, Coimbra, Portugal

Rui Bernardes

Association for Innovation and Biomedical Research on Light and Image (AIBILI), Coimbra, PortugalInstitute of Biomedical Research on Light and Image (IBILI), Faculty of Medicine, University of Coimbra, Coimbra, Portugal

José Cunha-Vaz

Association for Innovation and Biomedical Research on Light and Image (AIBILI), Coimbra, Portugal

Purpose: :
To identify different phenotypes in mild non-proliferative diabeticretinopathy (NPDR) in type-2 diabetic patients based on non-invasiveophthalmological examinations using cluster analysis.

Methods: :
Four-hundred and twelve (412) type-2 diabetic patients withmild NPDR were included in a 2-year observational and prospectivestudy to establish the association between phenotypes and genotypesin NPDR. The 258 patients that completed the first 6-month offollow-up underwent: color fundus photography (CFP), opticalcoherence tomography (Stratus OCT, Carl Zeiss Meditech Inc.)and blood tests. Data from baseline and the 6-month visit wasused in this analysis. The microaneurysm formation rate (MAFR)was computed from CFP using an automatic method for MA earmarking(RetmarkerDR, Critical Health SA). Retinal thickness (RT) mapswere computed using proprietary software allowing for the RTvalue in the central 500 µm in diameter macular area tobe computed. A cluster analysis was performed to identify earlyDR phenotypes using a non-hierarchical clustering method (Ward’sMethod). The identified clusters (phenotypes) were thereaftercorrelated with the progression of DR to clinically significantmacular edema (CSME).

Results: :
The clustering solution suggests the existence of 3 differentphenotypes of DR. One cluster (Phenotype 1) is characterizedby normal values on both the MAFR and the RT (median values:0 MA/year and 161.0 µm, respectively), the second cluster(Phenotype 2) is characterized by a high RT (median value: 192.7µm), and the third cluster (Phenotype 3) is characterizedby a high MAFR (median value: 5 MA/year). Thirteen (13) outof the 258 patients (5.0%) developed CSME after the 6-monthperiod (10 from Phenotype 2 (11.5%) and 3 from Phenotype 3 (2.7%),P=0.021). Patients from phenotypes 2 and 3 presents a higherrisk for DR progression to CSME (RR=1.571; 95%CI=[1.429; 1.728]).

Conclusions: :
Cluster analysis based on non-invasive techniques (color fundusphotography and OCT) identified 3 different phenotypes of earlyDR confirming the previous findings from our research groupin a different study/group of patients. Patients with high RTand/or high MAFR present a higher risk for DR progression toCSME (RR=1.571; 95%CI=[1.429; 1.728]).